In general, a gas turbine comprises vanes which are connected via a drive lever to a unison ring. The unison ring with its lever arrangement is typically found in the compressor section of the gas turbine, but may also be used in the turbine section of the gas turbine, e.g. the power turbine section. Possible connection means for connecting the drive lever to the unison ring are nuts and bolts, screwed hinge pins or secured pins, in particular cir-clip secured pins.
U.S. Pat. No. 4,979,874 discloses a variable vane drive mechanism, particularly discloses a drive arm lever which extends from the unison ring to a post at the outward end of a corresponding trailing edge segment. Each lever arm has a vane post end and a unison ring end. The unison ring end of each lever arm is attached to the unison ring by means, such as a bolt and a nut. The unison ring end of the lever arm is rotatable about the bolt.
U.S. Pat. No. 5,492,446 discloses a self-aligning variable stator vane including an airfoil with an integral outer trunnion having a seat extending integrally therefrom. A threaded stem extends from the seat and includes a coextensive alignment surface that cooperates with a complementary mounting hole in a lever arm which restrains rotation of the lever arm about the stem during assembly for ensuring a predetermined rotational orientation between the lever arm and the airfoil.
U.S. Pat. No. 6,802,692 discloses a device for controlling a variable-angle vane for a stator of a turbomachine compressor. The device comprises a link, connection means forming a hinge between a first end of the link and a control ring, fixing means for fixing a second end of the link on a pivot of a vane to be controlled, and pinch means acting transversely relative to a longitudinal midplane of the link to lock the second end of the link in rotation without slack on the pivot.
U.S. Pat. No. 3,356,288 discloses an axial flow compressor comprising an outer casing, inner frame members, and adjustable compressor stages. Each stage comprises a row of stator blades and a row of rotating compressor blades. The stator blades are each mounted by stud shafts journaled in the outer casing and inner frame respectively for pivotal movement about an axis extending radially from the center of rotation of a rotor. An end of a lever arm is secured to each stud and the other end of the lever arm is secured in an actuator ring using a pin which is retained on the actuator ring by a snap ring.
GB 837,649 discloses an axial-flow compressor having radially directed stator blades mounted on a casing for rotation about their axes by means of actuating rings encircling the casing and connected by levers to the bases of the blades. The rings are connected to the levers by universal joints, and the levers are secured to the bases of the blades, relative rotation between the levers and their blades being prevented by tangs on the bases received within openings in the levers.
There may be a need to provide a drive lever arrangement and method of placing a drive lever pin in a drive lever arrangement that allows for a quick and easy assembling and disassembling of parts of the drive lever arrangement, e.g. for maintenance and service.